method of glucose measurment

HbA1c Formation

• Glucose reacts with the amino group of Hemoglobin (Hb A1) to form a ketoamine.
• This reaction occurs non-enzymatically, attaching glucose to the Hb molecule.

HbA1c Normal Values and Sample Stability

• Normal HbA1c values range from 4-6%.
• No fasting is required for patients before taking HbA1c samples.
• Samples are stable for up to 1 week.

Calculating Average Glucose from HbA1c

• Average glucose can be calculated using the HbA1c result and the formula: 𝑒𝐴𝐺 (𝑚𝑔/𝑑𝐿) = 28.7 × 𝐻𝑏𝐴1𝑐 − 46.7

HbA1c Formation

• Glucose reacts with the amino group of Hemoglobin (Hb A1) to form a ketoamine.
• This reaction occurs non-enzymatically, attaching glucose to the Hb molecule.

HbA1c Normal Values and Sample Stability

• Normal HbA1c values range from 4-6%.
• No fasting is required for patients before taking HbA1c samples.
• Samples are stable for up to 1 week.

Calculating Average Glucose from HbA1c

• Average glucose can be calculated using the HbA1c result and the formula: 𝑒𝐴𝐺 (𝑚𝑔/𝑑𝐿) = 28.7 × 𝐻𝑏𝐴1𝑐 − 46.7

Glucose Measurement

• Glucose concentration can be measured in serum, plasma, or whole blood
• Whole blood glucose concentration is approximately lower than in plasma
• Fasting Plasma Glucose (FPG) levels are higher in the morning compared to the afternoon and night due to diurnal variation
• FPG testing should be conducted in the morning to account for this variation
• Patients must fast for 8-10 hours (not exceeding 16 hours) prior to testing
• It is essential to ask the patient about the exact time of their last meal before testing
• Urine glucose measurement is not a reliable method and is not used

Copper Reduction Methods

• Glucose acts as a reducing agent for copper
• Reaction of glucose with arsenomolybdic acid produces arsenomolybdenum blue
• This reaction is utilized in Clinitest tablets for glucose detection

Iron Reduction Methods

• Glucose acts as a reducing agent for iron
• Reaction of glucose with ferricyanide (yellow) produces ferrocyanide (colorless)
• This method is known as the Ferric reduction method (Hagedorn-Jensen method)

Ortho-Toluidine Method (Dubowski Method)

• Glucose reacts with aromatic amines to form Schiff bases, resulting in a green color
• This reaction is used for glucose detection

Affinity Chromatography HbA1c Measurement Preferred method of measurement The glycosylated hemoglobin (A1c) attaches to the boronate group of the resin and is selectively eluted from the resin bed using a buffer. This method is not temperature dependent. Not affected by hemoglobin F, S, or C.

Affinity Chromatography HbA1c Measurement Preferred method of measurement The glycosylated hemoglobin (A1c) attaches to the boronate group of the resin and is selectively eluted from the resin bed using a buffer. This method is not temperature dependent. Not affected by hemoglobin F, S, or C.

Sample Types for Ketone Detection

• Samples can be either serum or urine for ketone detection.

Gerhardt's Method

• Uses ferric chloride reacted with acetoacetic acid to produce a red color.
• Ferric chloride is the key reactant in this method.

Sodium Nitroprusside Method

• Reacts with acetoacetic acid in an alkaline pH to form a purple color.
• Alkaline pH is a necessary condition for this method to work.

Enzymatic Method

• Uses 3-hydroxybutyrate dehydrogenase to detect either 3-b-hydroxybutyric acid or acetoacetic acid.
• 3-hydroxybutyrate dehydrogenase is the enzyme involved in this method.

Microalbuminuria and Kidney Damage

• High glucose levels can damage kidneys, but before that, patients experience microalbuminuria, characterized by an increased albumin-creatinine ratio.
• To diagnose microalbuminuria, 2-3 urine specimens are collected within a 3-6 month period, and if all are abnormal, the patient is considered to have microalbuminuria.
• Microalbuminuria is a crucial early sign of nephropathy, preceding the development of creatinuria.
• There are three methods to measure albumin-creatinine ratio:

  Methods for Albumin-Creatinine Ratio Measurement

  • Random Spot Collection
  • 24-Hour Collection
  • Timed 4-Hour Overnight Collection

Factors Affecting Urine Albumin

• Exercise within 24 hours can increase urine albumin
• Infection can increase urine albumin
• Fever can increase urine albumin
• CHF (Congestive Heart Failure) can increase urine albumin
• Marked hyperglycemia can increase urine albumin
• Marked hypertension can increase urine albumin

Microalbuminuria

• Defined as persistent albuminuria in two out of three urine collections
• Characterized by: • 30-300 mg/24 h urine albumin excretion • 20-200 µg/min urine albumin excretion rate • Albumin-creatinine ratio of 30-300 µg/mg creatinine

Clinical Proteinuria/Macroalbuminuria

• Established with: • Albumin-creatinine ratio ≥300 mg/24 h • Urine albumin excretion rate >200 µg/min • Albumin-creatinine ratio ≥300 µg/mg